I agree with Rajeev's plan. One thing to bear in mind (its in the mails but might not jump out) is that some I/O applications may need an MPI_Offset sized datatype extent (HDF5 might be in this group). Bill On May 6, 2008, at 4:41 PM, Rajeev Thakur wrote:
I think we should come up with a plan ourselves before discussing with IBM. Something that involves minimal changes to their code would be best, so that it is less work for us. Let me digest all the various mails on this topic, look at what IBM has done, and then come back...
Rajeev
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Pavan Balaji Sent: Tuesday, May 06, 2008 4:07 PM To: [email protected] Subject: Re: [mpich2-core] BG/P patches
So, while we need not use IBM's exact fixes, we should fix it in some way -- whatever way we think is right. We can then try to propagate those fixes back to IBM.
Would it make sense to initiate a discussion with IBM about this, or is it too early?
I personally feel that we should internally use MPI_Offset instead of MPI_Aint for datatypes and I/O to calculate the total size and leave the rest (parts that are broken in the MPI standard) as they currently are. Specifically, anything that returns an MPI_Aint to the user might overflow on 32-bit systems (technically even on 64-bit systems, but we are some time away for that). But in cases where the user doesn't use such functions but MPICH2 internally has to evaluate the size, it should work fine.
-- Pavan
-- Pavan Balaji http://www.mcs.anl.gov/~balaji
William Gropp Paul and Cynthia Saylor Professor of Computer Science University of Illinois Urbana-Champaign